Rapid flow microfluorometry and other conventional cytokinetic tools (labelled precursor uptake) are used to study the effect of cancer chemotherapeutic agents on the cell cycle traverse and cyclephase sensitivity of tumor cells and target tissues (Bone marrow). These studies include cytokinetic alterations induced by methotrexate (high-dose) and various rescue agents (citrovorum factor, thymidine) and adriamycin and its analogs. Clinical studies are focussed on patients with solid tumors while experimental studies use mice bearing L 1210, P 388 and B16 melanomas, as well as athymic mice with human heterotransplants.